Method and apparatus for adjusting a gain of a receiver in a wireless device

ABSTRACT

A system including a first power measuring module, a gain control module, and a signal processing module. The first power measuring module is configured to generate a first power measurement of a signal received by a receiver of a wireless device based on a plurality of reference signals received in the signal by the receiver of the wireless device. Each of the plurality of reference signals is transmitted at a predetermined power. The first power measurement is generated in frequency domain. The first power measurement is generated during a first frame of the signal received by the receiver of the wireless device. The gain control module is configured to adjust a gain of the receiver of the wireless device based on the first power measurement. The signal processing module is configured to process a second frame in the signal subsequent to the first frame at the adjusted gain.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present disclosure is continuation of U.S. patent application Ser.No. 13/101,628 (now U.S. Pat. No. 8,773,966), filed on May 5, 2011,which claims the benefit of U.S. Provisional Application No. 61/332,601,filed on May 7, 2010. The entire disclosures of the applicationsreferenced above are incorporated herein by reference.

FIELD

The present disclosure relates generally to communication systems andmore particularly to signal power measurement and automatic gain controlin orthogonal frequency division multiple access (OFDMA) systems.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

In many communication systems, transmitters encode and modulate signalsbefore transmission, and receivers demodulate and decode receivedsignals. Many receivers use some form of automatic gain control toadjust gain of one or more receiver components so that the receivedsignals can be correctly demodulated and decoded.

SUMMARY

A receiver of a wireless communication device, the receiver including afast Fourier transform module, a first power measuring module, and again control module. The fast Fourier transform module is configured toconvert a signal from a time domain to a frequency domain. The signalincludes a plurality of reference signals. The reference signals have apredetermined power. The first power measuring module is configured togenerate a first power measurement of the signal in the frequency domainbased on the plurality of reference signals. The gain control module isconfigured to adjust a gain of the receiver based on the first powermeasurement.

A method for a receiver of a wireless communication device, the methodincluding converting a signal received by the receiver from a timedomain to a frequency domain. The signal includes a plurality ofreference signals. The reference signals have a predetermined power. Themethod further includes generating a first power measurement of thesignal in the frequency domain based on the plurality of referencesignals and adjusting a gain of the receiver based on the first powermeasurement.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of a receiver of a wirelesscommunication device, where the receiver sets a gain of one or morereceiver components based on signal power measured in the time domain;

FIG. 2 depicts an example of a long term evolution (LTE) sub-frame;

FIGS. 3A and 3B depict examples of gain variation in a receiver when thegain of the receiver components is set based on signal power measured inthe time domain;

FIG. 4A is a functional block diagram of a receiver that sets the gainof the receiver components based on signal power measured in thefrequency domain;

FIG. 4B is a functional block diagram of a receiver that sets the gainof the receiver components based on signal power measured in at leastone of the time domain and the frequency domain;

FIGS. 5A and 5B depict examples of gain variation in a receiver when thegain of the receiver components is set based on signal power measured inthe frequency domain; and

FIG. 6 is a flowchart of a method for setting the gain of the receivercomponents based on signal power measured in at least one of the timedomain and the frequency domain.

DESCRIPTION

The following description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Forpurposes of clarity, the same reference numbers will be used in thedrawings to identify similar elements. As used herein, the phrase atleast one of A, B, and C should be construed to mean a logical (A or Bor C), using a non-exclusive logical OR. It should be understood thatsteps within a method may be executed in different order withoutaltering the principles of the present disclosure.

As used herein, the term module may refer to, be part of, or include anApplication Specific Integrated Circuit (ASIC); an electronic circuit; acombinational logic circuit; a field programmable gate array (FPGA); aprocessor (shared, dedicated, or group) that executes code; othersuitable components that provide the described functionality; or acombination of some or all of the above, such as in a system-on-chip.The term module may include memory (shared, dedicated, or group) thatstores code executed by the processor.

The term code, as used above, may include software, firmware, and/ormicrocode, and may refer to programs, routines, functions, classes,and/or objects. The term shared, as used above, means that some or allcode from multiple modules may be executed using a single (shared)processor. In addition, some or all code from multiple modules may bestored by a single (shared) memory. The term group, as used above, meansthat some or all code from a single module may be executed using a groupof processors. In addition, some or all code from a single module may bestored using a group of memories.

The apparatuses and methods described herein may be implemented by oneor more computer programs executed by one or more processors. Thecomputer programs include processor-executable instructions that arestored on a non-transitory tangible computer readable medium. Thecomputer programs may also include stored data. Non-limiting examples ofthe non-transitory tangible computer readable medium are nonvolatilememory, magnetic storage, and optical storage.

The present disclosure relates to an automatic gain control in areceiver of a wireless device, where the receiver sets the gain ofreceiver components based on signal power measured in the frequencydomain. Specifically, the automatic gain control measures the signalpower in frequency domain based on reference signals (pilots) includedin a received sub-frame. At the end of the sub-frame, the automatic gaincontrol adjusts the gain of the receiver components according to themeasured signal power. The receiver processes the subsequent sub-frameaccording to the adjusted gain. While the automatic gain controlmeasures the signal power in frequency domain during a sub-frame, theautomatic gain control adjusts the gain of the receiver componentsaccording to the measured signal power at a sub-frame boundary thatfollows.

Referring now to FIG. 1, a receiver 100 of a wireless communicationdevice is shown. The receiver 100 uses AGC to set gain of the receivercomponents according to signal power measured in the time domain. Thereceiver 100 includes an antenna 102, an analog front-end (AFE) module104, an analog-to-digital converter (ADC) module 106, a first digitalsignal processing (DSP) module 108, a filter module 110, a downconvertermodule 112, a second DSP module 114, a fast Fourier transform (FFT)module 116, an automatic gain control (AGC) module 118, and the timedomain (TD) power measurement module 120. The receiver 100 receivessignals via the antenna 102. Although one antenna is shown, the receiver100 may include a plurality of antennas. For example, the plurality ofantennas may be arranged in a multiple-input multiple-output (MIMO)configuration.

The AFE module 104 processes the signals received via the antenna 102.For example, the AFE module 104 may demodulate the signals received viathe antenna 102. The ADC module 106 converts an output of the AFE module104 from analog to digital format. The first DSP module 108 processes anoutput of the ADC module 106. The filter module 110 filters an output ofthe first DSP module 108. For example, the filter module 110 may includea low-pass filter module.

The downconverter module 112 downconverts an output of the filter module110. The second DSP module 114 processes an output of the downconvertermodule 112. The FFT module 116 converts an output of the second DSPmodule 114 from the time domain to frequency domain. An output of theFFT module 116 is further processed by other modules (not shown) of thereceiver 100 in frequency domain. For example, a channel estimationmodule (not shown) of the receiver 100 may generate a channel estimatebased on the output of the FFT module 116.

The AGC module 118 controls the gain of the AFE module 104, the firstDSP module 108, and the second DSP module 114. The TD power measurementmodule 120 measures the signal power of the received signals in the timedomain and outputs the signal power measurement to the AGC module 118.The AGC module 118 adjusts the gain of the AFE module 104, the first DSPmodule 108, and the second DSP module 114 based on the signal powermeasurement in the time domain.

In systems such as Worldwide Interoperability for Microwave Access(WiMAX) systems using orthogonal frequency division multiplexing (OFDM),data are transmitted in frames. Each frame includes a plurality of OFDMsymbols. A first OFDM symbol of a frame includes a preamble. When areceiver receives a frame, the signal power of the frame is measuredwithin a cyclic prefix (CP) of the preamble present in the first OFDMsymbol of the frame. The gain of the receiver components is setaccording to the signal power measured based on the preamble in the timedomain.

The preamble facilitates signal power measurements due to the followingproperties of the preamble. The signal power of the preamble isunchanged across the frames. Further, since no data other than thepreamble is carried in the first OFDM symbol, the signal power measuredbased on the preamble does not depend on resource allocation, which cancause variation in signal power measured based on data symbols in theframes. Further, the preamble is a wideband signal with a time-domainsignal power variation contained within a ±3 dB range in the CP.Accordingly, any errors in setting the gain and decoding data in theframes are limited to ±3 dB.

Frames of many OFDMA systems such as Long Term Evolution (LTE) systemsspecified by 3rd Generation Partnership Project (3GPP), however, may notinclude signals like the preamble in the WiMAX systems. Accordingly, inthese systems, the signal power measurements may have to be based onsymbols that carry user data. Measuring signal power based on user datapresents the following problems.

Depending on the amount of user data carried in the frames, narrow bandallocations are likely to occur. Measuring narrow band signal power in asmall measurement window (e.g., within CP), however, can cause largeerrors in signal power measurements. Hence, the signal power must bemeasured in a larger window (e.g., within a sub-frame or severalsub-frames). Additionally, based on the amount of user data, resourceallocation across the frames may vary dynamically. Dynamic resourceallocation may result in OFDM symbols with varying time-domain symbolpowers across the frames. Accordingly, a gain setting derived fromsignal power measured based on data in one frame may not be suitable forprocessing a subsequent frame.

Referring now to FIG. 2, an example of an LTE sub-frame is shown. Dataare located in the LTE sub-frame in increments of one resource block(RB). A resource block includes a predetermined number of sub-carriers(e.g., 1 RB=12 sub-carriers). The LTE sub-frame does not includepreamble. Instead, the LTE sub-frame includes reference signals, whichare also called pilot signals or pilots. In the example shown, the LTEsub-frame includes two reference signals per resource block (i.e., onereference signal (RS) for every six sub-carriers). The number ofreference signals per resource block is proportional to the number ofantennas in the receiver.

In the LTE sub-frame, symbols carrying the reference signals and userdata are called RS symbols, and symbols carrying user data and noreference signals are called data symbols. An RS symbol includes bothreference signals and user data, each occupying different sub-carriers(frequencies). Each LTE sub-frame can include a plurality of RS symbolsand a plurality data symbols as shown. In an RS symbol, a ratio of anumber of RS sub-carriers (i.e., a number of sub-carriers used to carrythe reference signals) in a resource block to a total number ofsub-carriers in the resource block is called a reference signal density.

The LTE sub-frame includes a control channel region and a data channelregion. A first plurality of symbols in the LTE sub-frame is in thecontrol channel region. A second plurality of symbols in the LTEsub-frame is in the data channel region. In the example shown, twocontrol channels (control 1 and control 2) and two data channels (data 1and data 2) are allocated in the LTE sub-frame. The control channel 1(control 1) controls resource allocation of the data channel 1 (data 1),and the control channel 2 (control 2) controls resource allocation ofthe data channel 2 (data 2). In general, one or more control channelsand one or more data channels may be used. Signal power in the controlchannel region is not representative of the signal power in the datachannel region.

Narrow band allocation in OFDMA systems causes large variation in timedomain signal power estimates. Specifically, since signal power varieswithin a symbol, the signal power measurement may differ depending on asize of a measurement window used to measure the signal power. Forexample, the signal power measured using a measurement window of sizeCP/4 can be different than the signal power measured using a measurementwindow of size CP/2 or 3CP/4.

In other words, signal power estimation is a function of a window lengthand signal properties. A small measurement window tends to yield aninstantaneous signal power estimate instead of an average signal powerestimate. Accordingly, errors in signal power measurement can bepronounced when small measurement windows are used to measure signalpower. Data can be lost if gain is set according to erroneous signalpower measurements.

Further, even if the number of gain updates is limited to one, and afull CP is used for signal power measurement to reduce the error, thevariation in the signal power measurement precludes the AGC module fromupdating the gain within a CP based on the signal power measured in thecurrent symbol. In other words, without the preamble, signal powercannot be measured reliably based on the first symbol of a sub-frame,and gain to process the sub-frame cannot be set correctly based on thesignal power measured during the first symbol of the sub-frame.Specifically, in the time domain, by the time signal power is measuredbased on the first symbol, the first symbol is lost. Accordingly, signalpower must be measured in a previous sub-frame, and gain to process asubsequent sub-frame must be set based on the signal power measured inthe previous sub-frame.

Signal power measured in a previous sub-frame, however, cannot be usedto set the gain to process a subsequent frame because resourceallocation may differ from one frame to another. Consequently, thesignal power may also differ from one frame to another. As a result, again setting derived from the signal power measured in a previoussub-frame cannot be used to process a subsequent sub-frame.

For example, an empty sub-frame allocation results in empty OFDMsymbols, which yield very small power estimates that should be excludedwhen setting the gain. This, together with the fact that the gain toprocess a current sub-frame is set based on the signal power measured ina previous sub-frame, precludes symbol by symbol gain adjustment in AGCtracking.

Accordingly, the time domain power measurements should be aggregatedover a longer measurement window (e.g., over one or more sub-frames inLTE systems). Combining power measurements of symbols in one or moresub-frames in AGC tracking, however, circumvents power fluctuation fromsymbol to symbol but does not address power fluctuation from sub-frameto sub-frame due to difference in loading (e.g., empty sub-framefollowed by fully loaded sub-frame).

Referring now to FIGS. 3A and 3B, examples of gain variation when gainis set based on a time domain power measurement from a precedingsub-frame are shown. The examples shown are for gain variation in anAWGN channel (i.e., a channel with no channel gain change) in order toisolate signal power changes due to changes in resource allocation fromthe changes in channel gains. In the examples, a gain offset (GO)indicates a gain error in a sub-frame.

In FIG. 3A, the AGC module begins gain control with an initial gainsetting, and a first sub-frame received is empty (i.e., no load). TheAGC module measures signal power in a previous sub-frame and sets thegain to process the following sub-frame based on the signal powermeasured in the previous sub-frame as shown. Note that the gainvariation is worse when an empty sub-frame is followed by a fully loadedsub-frame.

In FIG. 3B, the AGC module begins with an initial gain setting, and afirst subframe received is full (i.e., full load). The AGC modulemeasures signal power in a previous sub-frame and sets the gain toprocess the following sub-frame based on the signal power measured inthe previous sub-frame as shown. As FIGS. 3A and 3B indicate, differentloading of the sub-frames causes large gain variation, and time-domainpower measurements alone are insufficient for proper AGC tracking.

The present disclosure relates to measuring signal power based onreference signals (pilots) included in a sub-frame and setting the gainof the receiver components that process the sub-frame based on thesignal power measured based on the reference signals in frequencydomain. Each sub-frame includes the reference signals at predeterminedlocations (called resource elements) in time and frequency as shown inFIG. 2. Note that the reference signals are different than a preamble, acyclic prefix, a guard band, a sub-carrier, a training signal, and userdata. Rather, to facilitate channel estimation at the receiver, thereference signals are specifically transmitted with a predeterminedsignal power that is independent of resource allocation in thesub-frame. Further, the resource signals cover the full bandwidth andare therefore particularly suitable for accurately estimating signalpower at the receiver.

Additionally, no extra processing is required at the receiver to extractthe reference signals for measuring signal power since the referencesignals are automatically extracted by the FFT module of the receiverfor channel estimation. Accordingly, the reference signals are readilyavailable for measuring signal power in the frequency domain. Thepresent disclosure relates to measuring the signal power in thefrequency domain based on the reference signals and setting the gain ofthe receiver components based on the frequency domain signal powermeasurement. The time domain signal power measurement is combined withthe frequency domain signal power measurement to set the gain of thereceiver components. Both time and frequency domain signal powermeasurements are used since most wireless receivers operate in presenceof blockers (e.g., narrow band blockers, adjacent and non-adjacentchannel blockers, etc.), and most RF receivers do not completely filterout signals outside of the channel of interest.

Referring now to FIG. 4A, a receiver 200 of a wireless communicationdevice is shown. The receiver 200 uses AGC to set gain of the receivercomponents according to signal power measured in the frequency domain.The receiver 200 includes the antenna 102, the analog front-end (AFE)module 104, the analog-to-digital converter (ADC) module 106, the firstdigital signal processing (DSP) module 108, the filter module 110, thedownconverter module 112, the second DSP module 114, the fast Fouriertransform (FFT) module 116, an automatic gain control (AGC) module 202,and a frequency domain (FD) power measurement module 204.

The AGC module 202 controls the gain of the AFE module 104, the firstDSP module 108, and the second DSP module 114 (collectively referred toas the receiver components). The FD power measurement module 204measures the signal power of the received signals in frequency domain asexplained below and outputs the signal power measurement to the AGCmodule 202. The AGC module 202 adjusts the gain of the receivercomponents based on the signal power measurement in frequency domain.

Mathematically, a relationship between time-domain root mean square(RMS) of a received signal and frequency-domain RMS of the receivedsignal can be expressed by the following equation (assuming full loadingwith equal sub-carrier powers):

${RMS}_{{TD}_{i}}^{2} = {{\frac{1}{N}{\sum\limits_{n = 0}^{N - 1}\;{{y_{i}(n)}}^{2}}} = {{\frac{1}{N^{2}\;}{\sum\limits_{k \in \Omega_{sc}}\;{{Y_{i}(k)}}^{2}}} = {\frac{1}{\rho_{RS} \cdot N^{2}}{\sum\limits_{k \in \Omega_{RS}}^{}\;{{Y_{i}(k)}}^{2}}}}}$In the equation, y_(i)(n) denotes the received signal in the timedomain, and Y_(i)(k) denotes the received signal in frequency domain.ρ_(RS) denotes a reference signal density (i.e., a ratio of number of RSsub-carriers in a resource block to a total number of sub-carriers inthe resource block as defined earlier). For example, in FIG. 2,ρ_(RS)=1/6 since two reference signals are used per resource block of 12sub-carriers (i.e., 1 reference signal is used every six sub-carriers).N denotes FFT size (e.g., N=512, 1024, etc.). Ω_(sc) denotes a set ofsub-carriers used (which may differ from the FFT size), and Ω_(RS)denotes a set of reference signal sub-carriers. i denotes a receiveantenna index (e.g., i can be 0 or 1 for two receive antennas). Notethat the signal power equals RMS₂ divided by a termination impedance.

The FD power measurement module 204 measures the frequency-domain RMS ofRS sub-carriers for each receive antenna i over RS sub-carriers in eachRS symbol m. The FD power measurement module 204 can perform themeasurement within a predetermined measurement interval. For example,the predetermined measurement interval can be one or more LTEsub-frames. The FD power measurement module 204 measures thefrequency-domain RMS of RS sub-carriers for each receive antenna i overRS sub-carriers in each RS symbol m within the predetermined measurementinterval based on the following equation:

${{RMS}_{RS}^{2}\left( {i,m} \right)} = {\frac{1}{N^{2}}{\sum\limits_{k \in \Omega_{RS}}\;{{Y_{i,m}(k)}}^{2}}}$Note that the FD power measurement module 204 measures thefrequency-domain RMS of RS sub-carriers only based on RS symbols and notbased on data symbols (shown in FIG. 2).

The FD power measurement module 204 averages the frequency-domain RMS ofRS sub-carriers measured as above over all N_(RS) RS symbols in thepredetermined measurement interval using the following equation:

${RMS}_{RS}^{2} = {\max\limits_{i}{\frac{1}{N_{RS}}{\sum\limits_{m = 0}^{N_{{RS}^{- 1}}}\;{{RMS}_{RS}^{2}\left( {i,m} \right)}}}}$In some systems, a single AGC may control the gain of the receivercomponents that process signals received via multiple antennas. In suchsystems, the FD power measurement module 204 finds a maximum of theaveraged signal powers measured for the i antennas as indicated above.The FD power measurement module 204 uses the maximum to set the gain ofthe receiver components.

In systems where a separate AGC is used to set the gain of the receivercomponents that process signals received via each antenna, the maximumis not used. Instead, the averaged signal power for each antennacalculated as above is used to set the gain of the receiver componentsassociated with the respective antenna.

The AGC module 202 generates a frequency domain gain offset (GO_(FD)),which is an amount by which the AGC module 202 adjusts the gain of thereceiver components, using the following equation:GO_(FD)=10 log₁₀(RMS_(RS) _(target) ²/RMS_(RS) ^(S))RS_(RS) _(target) ²=ρ_(RS)·RMS_(TD) _(target) ²In the equation, values that are subscripted with the word “target”indicate respective desired values. The AGC module 202 can alsodetermine the gain offset GO_(FD) using a lookup table.

Setting the gain based on the signal power measured in the time domainensures a constant total signal power. In contrast, setting the gainbased on the signal power measured in frequency domain ensures aconstant power spectral density (i.e., constant signal power infrequency domain) regardless of resource allocation. For example, thesignal power measured in frequency domain is unchanged regardless of thewhether one resource block or 100 resource blocks are allocated in anLTE sub-frame. Accordingly, the output of the FFT module 116 isunchanged even when the output of the time-domain power measurementmodule 120 changes due to changes in resource allocation.

Referring now to FIG. 4B, a receiver 201 of a wireless communicationdevice is shown. The receiver 201 uses AGC to set gain of the receivercomponents according to signal power measured in frequency domain andthe time domain. The receiver 201 includes all the modules of thereceiver 200 and additionally includes the time-domain power measurementmodule 120. Frequency-domain power measurement described aboveaccurately measures power within a desired channel bandwidth and issufficient if signals outside of desired channel bandwidth (i.e.,blockers) are not present. Further, the frequency domain powermeasurement works equally well on both AWGN and fading channels in theabsence of blockers. Blockers from adjacent channels, however, canadversely impact the output of the ADC module 106 if the blockers arenot filtered out effectively. Accordingly, the time-domain powermeasurement should be combined with the frequency-domain powermeasurement to set the gain of the receiver components.

Specifically, the AGC module 202 should select a minimum of thefrequency domain gain offset and the time domain gain offset GO_(TD) andshould use the minimum to set the gain of the receiver components. TheAGC module 202 determines the time-domain gain offset GO_(TD) based onthe total signal power in the time domain measured by the time-domainpower measurement module 118 and a desired signal power. Combining timeand frequency domain power gain offsets is mathematically expressed bythe following equation:GO=min(GO_(TD),GO_(FD))Accordingly, the AGC module 202 will set the gain of the receivercomponents based on a greater of the frequency-domain power measurementand the time-domain power measurement to minimize the effect of blockerson the output of the ADC module 106.

Referring now to FIGS. 5A and 5B, examples of gain variation when gainis set based on a frequency-domain power measurement from a precedingsub-frame are shown. The examples shown are for gain variation inabsence of residual blocker power in an additive white Gaussian noise(AWGN) channel (i.e., a channel with no channel gain change) in order toisolate signal power changes due to changes in resource allocation fromthe changes in channel gains. In FIG. 5A, the AGC module 202 begins withan initial gain setting, and a first sub-frame received is empty (i.e.,no load). The AGC module 202 measures signal power in a previoussub-frame in frequency domain based on the reference signals in thesub-frame. Note that the reference signal RMS target defined earlier isselected such that, in absence of residual blocker power, frequencydomain gain offset is always equal to the time domain gain offset forfully allocated sub-frame regardless of the actual allocation. Thus,although the first sub-frame received is empty, the AGC module 202 willdecrease the gain to a level necessary to process a fully allocatedsub-frame as shown.

After the gain is set, assuming blockers are filtered, the AGC module202 does not need to change the gain to process subsequent sub-frames.This is because the AGC module 202 sets the gain according to signalpower measured based on the reference signals independently of resourceallocation of the sub-frame in which the signal power is measured. Notethat the time-domain gain offset varies but is disregarded when settingthe gain (assuming blockers are filtered).

In FIG. 5B, the AGC module 202 begins with an initial gain setting, anda first sub-frame received is full (i.e., full load). The AGC module 202measures signal power in a previous sub-frame in the frequency domainbased on the reference signals in the sub-frame and sets the gain toprocess the following frame based on the signal power measured in theprevious frame as shown. As FIGS. 5A and 5B indicate, different loadingof the sub-frames does not causes large gain variation, and thefrequency-domain power measurement is sufficient for AGC tracking whenblockers are filtered.

In summary, setting the gain of the receiver components by measuringsignal power in the frequency domain based on the reference signalseliminates gain fluctuation (errors) due to dynamic resource allocation.This can reduce bit width of receiver data path modules by at least twobits. For example, in LTE systems where gain can vary between 8 dB and13 dB, precision (i.e., dynamic range) of the ADC module 106 andprecision of other time-domain and frequency-domain data processingcircuits can be reduced by at least 2 bits, which would be otherwisenecessary to provide headroom for gain variation between 8 dB and 13 dB.Further, using time-domain and frequency domain power measurements toset gain prevents the output of the ADC module 106 from saturating incase of residual blocker leakage.

Referring now to FIG. 6, a method 300 for setting gain of receivercomponents of a wireless communication device is shown. Control beginsat 302. At 304, control measures signal power in frequency domain basedon reference signals in the received signal and the total signal powerin the time domain. At 306, control determines if the time or frequencydomain signal power is larger. At 308, if the frequency domain signalpower is larger, control sets the gain of the receiver components basedon the signal power measured in frequency domain based on the referencesignals, and control ends at 310. At 312, if the time domain signalpower is larger, controls sets the gain of the receiver components basedon the signal power measured in the time domain, and control ends at310.

The teachings of the present disclosure are applicable to all OFDMAsystems (e.g., WiMAX, LTE, etc.) since the power measurement and gainsetting disclosed herein relies only on reference signals. The teachingscan be further extended to other systems that use dynamic resourceallocation and that include signals similar to the pilots.

The broad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims.

What is claimed is:
 1. A system comprising: a first power measuringmodule configured to generate a first power measurement of a signalreceived by a receiver of a wireless device, the first power measurementof the signal being generated based on a plurality of reference signalsassociated with the signal received by the receiver of the wirelessdevice, wherein each of the plurality of reference signals istransmitted at a predetermined power, wherein the first powermeasurement is generated in frequency domain, and wherein the firstpower measurement is generated during a first frame of the signalreceived by the receiver of the wireless device; a second powermeasuring module configured to generate a second power measurement ofthe signal in time domain; a gain control module configured to adjust again of the receiver based on (i) the first power measurement and (ii)the second power measurement; and a signal processing module configuredto process a second frame in the signal, wherein the second frame issubsequent to the first frame, and wherein the signal processing moduleprocesses the second frame at the gain as adjusted by the gain controlmodule.
 2. The system of claim 1, wherein the second power measurementdepends on resource allocation used in the signal.
 3. The system ofclaim 1, wherein the signal processing module is configured to processthe second frame independently of resource allocation of framessubsequent to the first frame in the signal.
 4. The system of claim 1,further comprising: a second power measuring module configured togenerate a second power measurement of the signal in time domain,wherein the second power measurement depends on resource allocation usedin the signal, and wherein the gain control module is configured toadjust the gain of the receiver based on the first power measurementindependently of variation in the second power measurement.
 5. Thesystem of claim 1, wherein: the signal includes a plurality of referencesymbols and a plurality of data symbols; the first power measuringmodule is configured to measure a mean square power of a set of thereference signals in each of the reference symbols within a measurementinterval, generate the first power measurement by averaging the meansquare powers of the reference symbols, and generate an offset based onthe first power measurement and a desired power; and the gain controlmodule is configured to adjust the gain of the receiver based on theoffset.
 6. The system of claim 1, the receiver comprising: a secondpower measuring module configured to generate a second power measurementof the signal in time domain, wherein the second power measurementdepends on resource allocation used in the signal, and wherein the gaincontrol module is configured to generate a first offset based on thefirst power measurement and a desired power, generate a second offsetbased on the second power measurement and the desired power, and adjustthe gain of the receiver based on a smaller of (i) the first offset and(ii) the second offset.
 7. The system of claim 1, wherein: the referencesignals are present in the signal at predetermined locations; and thereference signals do not correspond to a preamble, a cyclic prefix, aguard band, a sub-carrier, a training signal, and user data.
 8. Thesystem of claim 1, wherein: the signal includes sub-carriers modulatedusing orthogonal frequency division multiplexing; and the referencesignals are pilot signals transmitted using a predetermined number ofthe sub-carriers.
 9. The system of claim 1, wherein the receiver isconfigured to generate a channel estimate based on the referencesignals.
 10. A method comprising: generating a first power measurementof a signal received by a receiver of a wireless device, the first powermeasurement being generated based on a plurality of reference signalsreceived associated with the signal received by the receiver of thewireless device, wherein each of the plurality of reference signals istransmitted at a predetermined power, wherein the first powermeasurement is generated in frequency domain, and wherein the firstpower measurement is generated during a first frame of the signalreceived by the receiver of the wireless device; generating a secondpower measurement of the signal in time domain; adjusting a gain of thereceiver based on (i) the first power measurement and (ii) the secondpower measurement; and processing a second frame in the signal at theadjusted gain, wherein the second frame in the signal is subsequent tothe first frame in the signal.
 11. The method of claim 10, wherein thesecond power measurement depends on resource allocation used in thesignal.
 12. The method of claim 10, further comprising the processing ofthe second frame independently of resource allocation of framessubsequent to the first frame in the signal.
 13. The method of claim 10,further comprising: generating a second power measurement of the signalin time domain, wherein the second power measurement depends on resourceallocation used in the signal; and adjusting the gain of the receiverbased on the first power measurement independently of variation in thesecond power measurement.
 14. The method of claim 10, wherein the signalincludes a plurality of reference symbols and a plurality of datasymbols, the method further comprising: measuring a mean square power ofa set of the reference signals in each of the reference symbols within ameasurement interval, generating the first power measurement byaveraging the mean square powers of the reference symbols, andgenerating an offset based on the first power measurement and a desiredpower; and adjusting the gain of the receiver based on the offset. 15.The method of claim 10, the receiver comprising: generating a secondpower measurement of the signal in time domain, wherein the second powermeasurement depends on resource allocation used in the signal;generating a first offset based on the first power measurement and adesired power; generating a second offset based on the second powermeasurement and the desired power; and adjusting the gain of thereceiver based on a smaller of (i) the first offset and (ii) the secondoffset.
 16. The method of claim 10, wherein: the reference signals arepresent in the signal at predetermined locations; and the referencesignals do not correspond to a preamble, a cyclic prefix, a guard band,a sub-carrier, a training signal, and user data.
 17. The method of claim10, wherein: the signal includes sub-carriers modulated using orthogonalfrequency division multiplexing; and the reference signals are pilotsignals transmitted using a predetermined number of the sub-carriers.18. The method of claim 10, further comprising generating a channelestimate based on the reference signals.